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The mass of a lift is 2000 kg. When the tension in the supporting cable is 28000 N, then its acceleration is
A
14 m $s^{-2}$ upwards
B
30 m $s^{-2}$ downwards
C
4 m $s^{-2}$ upwards
D
4 m $s^{-2}$ downwards
Detailed Solution
Forces on the lift: tension T = 28000 N upward and weight mg = 2000 × 10 = 20000 N downward (taking g = 10 m $s^{-2}$).
The tension is greater than the weight, so the net force and the acceleration are upward.
$T - mg = ma$
$a = \frac{T - mg}{m} = \frac{28000 - 20000}{2000}$
a = 4 m $s^{-2}$ upwards
The tension is greater than the weight, so the net force and the acceleration are upward.
$T - mg = ma$
$a = \frac{T - mg}{m} = \frac{28000 - 20000}{2000}$
a = 4 m $s^{-2}$ upwards